The opportunistic human pathogen P. aeruginosa utilizes N-acylhomoserine lactones as quorum sensing "autoinducers" to specifically induce numerous virulence genes. AiiA is the first enzyme known to inactivate N-acylhomoserine lactones. Expression of AiiA in transformed Erwinia carotovora strain SCG1 significantly reduces the release of AI, decreases extracellular pectolytic enzyme activities, and attenuates pathogenicity on potato, eggplant, Chinese cabbage, carrot, celery, cauliflower, and tobacco. Plants transgenic for AiiA are resistant to E. carotovora infection (Dong et al., 2001). Based on these proof-of-principle studies we shall link this enzyme to a human antibody heavy chain to create a stabilized molecule suitable for human use. In phase I we will make a chimaeric AiiA-Ig by fusing the cDNA of AiiA to the N terminus of the CHI of human IgG1. AiiA-Ig will be expressed in mammalian cells and the protein purified by affinity chromatography. Finally we will demonstrate the capacity of AiiA-Ig to attenuate P. aeruginosa virulence factor expression in vitro. In phase II we will demonstrate activity of AiiA-Ig to attenuate pathogenesis of P. aeruginosa infection in mouse models (eg. lung, sepsis, burn), prepare a deimmunized or PEG-linked form of AiiA-Ig suitable for human therapeutic use and begin to carry out preclinical pharmacology and toxicology studies with the lead molecule. PROPOSED COMMERCIAL APPLICATION: NOT AVAILABLE